/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2005 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package clojure.asm;

/**
 * A non standard class, field, method or code attribute.
 *
 * @author Eric Bruneton
 * @author Eugene Kuleshov
 */
public class Attribute{

/**
 * The type of this attribute.
 */
public final String type;

/**
 * The raw value of this attribute, used only for unknown attributes.
 */
byte[] value;

/**
 * The next attribute in this attribute list. May be <tt>null</tt>.
 */
Attribute next;

/**
 * Constructs a new empty attribute.
 *
 * @param type the type of the attribute.
 */
protected Attribute(final String type){
	this.type = type;
}

/**
 * Returns <tt>true</tt> if this type of attribute is unknown. The default
 * implementation of this method always returns <tt>true</tt>.
 *
 * @return <tt>true</tt> if this type of attribute is unknown.
 */
public boolean isUnknown(){
	return true;
}

/**
 * Returns <tt>true</tt> if this type of attribute is a code attribute.
 *
 * @return <tt>true</tt> if this type of attribute is a code attribute.
 */
public boolean isCodeAttribute(){
	return false;
}

/**
 * Returns the labels corresponding to this attribute.
 *
 * @return the labels corresponding to this attribute, or <tt>null</tt> if
 *         this attribute is not a code attribute that contains labels.
 */
protected Label[] getLabels(){
	return null;
}

/**
 * Reads a {@link #type type} attribute. This method must return a <i>new</i>
 * {@link Attribute} object, of type {@link #type type}, corresponding to
 * the <tt>len</tt> bytes starting at the given offset, in the given class
 * reader.
 *
 * @param cr      the class that contains the attribute to be read.
 * @param off     index of the first byte of the attribute's content in {@link
 *                ClassReader#b cr.b}. The 6 attribute header bytes, containing the
 *                type and the length of the attribute, are not taken into account
 *                here.
 * @param len     the length of the attribute's content.
 * @param buf     buffer to be used to call
 *                {@link ClassReader#readUTF8 readUTF8},
 *                {@link ClassReader#readClass(int,char[]) readClass} or
 *                {@link ClassReader#readConst readConst}.
 * @param codeOff index of the first byte of code's attribute content in
 *                {@link ClassReader#b cr.b}, or -1 if the attribute to be read is
 *                not a code attribute. The 6 attribute header bytes, containing the
 *                type and the length of the attribute, are not taken into account
 *                here.
 * @param labels  the labels of the method's code, or <tt>null</tt> if the
 *                attribute to be read is not a code attribute.
 * @return a <i>new</i> {@link Attribute} object corresponding to the given
 *         bytes.
 */
protected Attribute read(
		final ClassReader cr,
		final int off,
		final int len,
		final char[] buf,
		final int codeOff,
		final Label[] labels){
	Attribute attr = new Attribute(type);
	attr.value = new byte[len];
	System.arraycopy(cr.b, off, attr.value, 0, len);
	return attr;
}

/**
 * Returns the byte array form of this attribute.
 *
 * @param cw        the class to which this attribute must be added. This parameter
 *                  can be used to add to the constant pool of this class the items
 *                  that corresponds to this attribute.
 * @param code      the bytecode of the method corresponding to this code
 *                  attribute, or <tt>null</tt> if this attribute is not a code
 *                  attributes.
 * @param len       the length of the bytecode of the method corresponding to this
 *                  code attribute, or <tt>null</tt> if this attribute is not a code
 *                  attribute.
 * @param maxStack  the maximum stack size of the method corresponding to
 *                  this code attribute, or -1 if this attribute is not a code
 *                  attribute.
 * @param maxLocals the maximum number of local variables of the method
 *                  corresponding to this code attribute, or -1 if this attribute is
 *                  not a code attribute.
 * @return the byte array form of this attribute.
 */
protected ByteVector write(
		final ClassWriter cw,
		final byte[] code,
		final int len,
		final int maxStack,
		final int maxLocals){
	ByteVector v = new ByteVector();
	v.data = value;
	v.length = value.length;
	return v;
}

/**
 * Returns the length of the attribute list that begins with this attribute.
 *
 * @return the length of the attribute list that begins with this attribute.
 */
final int getCount(){
	int count = 0;
	Attribute attr = this;
	while(attr != null)
		{
		count += 1;
		attr = attr.next;
		}
	return count;
}

/**
 * Returns the size of all the attributes in this attribute list.
 *
 * @param cw        the class writer to be used to convert the attributes into byte
 *                  arrays, with the {@link #write write} method.
 * @param code      the bytecode of the method corresponding to these code
 *                  attributes, or <tt>null</tt> if these attributes are not code
 *                  attributes.
 * @param len       the length of the bytecode of the method corresponding to
 *                  these code attributes, or <tt>null</tt> if these attributes are
 *                  not code attributes.
 * @param maxStack  the maximum stack size of the method corresponding to
 *                  these code attributes, or -1 if these attributes are not code
 *                  attributes.
 * @param maxLocals the maximum number of local variables of the method
 *                  corresponding to these code attributes, or -1 if these attributes
 *                  are not code attributes.
 * @return the size of all the attributes in this attribute list. This size
 *         includes the size of the attribute headers.
 */
final int getSize(
		final ClassWriter cw,
		final byte[] code,
		final int len,
		final int maxStack,
		final int maxLocals){
	Attribute attr = this;
	int size = 0;
	while(attr != null)
		{
		cw.newUTF8(attr.type);
		size += attr.write(cw, code, len, maxStack, maxLocals).length + 6;
		attr = attr.next;
		}
	return size;
}

/**
 * Writes all the attributes of this attribute list in the given byte
 * vector.
 *
 * @param cw        the class writer to be used to convert the attributes into byte
 *                  arrays, with the {@link #write write} method.
 * @param code      the bytecode of the method corresponding to these code
 *                  attributes, or <tt>null</tt> if these attributes are not code
 *                  attributes.
 * @param len       the length of the bytecode of the method corresponding to
 *                  these code attributes, or <tt>null</tt> if these attributes are
 *                  not code attributes.
 * @param maxStack  the maximum stack size of the method corresponding to
 *                  these code attributes, or -1 if these attributes are not code
 *                  attributes.
 * @param maxLocals the maximum number of local variables of the method
 *                  corresponding to these code attributes, or -1 if these attributes
 *                  are not code attributes.
 * @param out       where the attributes must be written.
 */
final void put(
		final ClassWriter cw,
		final byte[] code,
		final int len,
		final int maxStack,
		final int maxLocals,
		final ByteVector out){
	Attribute attr = this;
	while(attr != null)
		{
		ByteVector b = attr.write(cw, code, len, maxStack, maxLocals);
		out.putShort(cw.newUTF8(attr.type)).putInt(b.length);
		out.putByteArray(b.data, 0, b.length);
		attr = attr.next;
		}
}
}
